The summit part of Mount Etna revealed by High Resolution DC Electrical Resistivity Tomography coupled with complementary geophysical and soil gas techniques

Between 25 June and 13 July 2015 a very deep ERT profile (Pole-Dipole configuration, 40m spacingbetween electrodes and a remote electrode located at ~10km from the acquisition points) has been performedin the framework of the “MED-SUV” Project. Self-potential, soil gas concentrations (CO2, 222Rn, 220Rn, He,H2 and CH4) and soil temperature measurements were coupled to the ERT profile with a spacing of 20m(except for Rn: 40m). The NE-SW profile crossed Etnas summit craters in the middle of the 5720m ERTtotal length. Six roll along protocols of . of the dispositive (600m out of 2520m tot) have been carried outand, for the first time, a high resolution DC ERT profile reached the noticeable investigation depth of 900mb.g.l.. The results clearly evidence the central shallow hydrothermal system of Mt. Etna with large positiveself-potential anomaly, high values of temperature, 222Rn, CO2, He, H2 and CH4, in the areas where theconductive bodies reach the surface in correspondence of the summit craters and the 2014 eruptive vents(CO2, 222Rn and temperature). Structural boundaries, such as the Elliptic Crater, were highlighted by a sharpdecrease of the self-potential inside the Elliptic Crater. The high activity of 220Rn (Thoron) outside theElliptic Crater highlights shallow gas source. The resistive body identified just below the NE crater isprobably due to the over-heated plume rising from the top of the shallow feeding system towards the surface.